<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="js/react.development.js"></script>
    <script src="js/react-dom.development.js"></script>
    <script src="js/babel.js"></script>
</head>
<body>
    <div id="root"></div>
<script type="text/babel">
function Header(){
    return (<header>
        <h1>Hello React</h1>
    </header>);
}
ReactDOM.render(
    <Header />, 
    document.querySelector("#root")
);
</script>      
</body>
</html>